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Author Topic: How to use a motor as a dynamo?  (Read 23310 times)
kaffemustasj
Gunner
**
Norway Norway


« on: June 29, 2009, 12:22:06 pm »

I have quite recently acquired a modell steamengine. It was a gift from my gf.
I tested it as soon as I had the possibility (which was yesterday, I am now getting ready for a new run Grin). Now, I really want it to power something, or rather give power to something.
To use a DC motor as a dynamo seems rather easy. So here comes my questions to you (and I have googled the subject several times), the wise people of brassgoggles:
1. Will the power generated from the motor/dynamo be AC?
2. What kind of motor will give the most output, 1.5v, 3v, 5v or 6v?
3. Is there anything I or some particular parts I should use to improve my output voltage?

Thank you for the help Grin
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Khem Caigan
Zeppelin Overlord
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United States United States


Aut Inveniam Viam Aut Faciam


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« Reply #1 on: June 29, 2009, 02:32:42 pm »

Ultra-Simple Electric Generator
Wire and Spinning Magnets

(c)1996 William Beaty
http://tinyurl.com/9r42h5

Model Steam Engine
and
Other Educational Motors

http://tinyurl.com/ny94nq

Model Steam Engine
Electric Generator DC

@YouTube
http://tinyurl.com/nu4p7t

Wilesco D-24 Powering
Electric Generator

@YouTube
http://tinyurl.com/kr3dtq

Wilesco D-24 Electrical
@YouTube
http://tinyurl.com/mplt5g

Electric Generator
for Model Steam Engine
( Jensen Wilesco Mamod )

http://tinyurl.com/mwau8g
« Last Edit: July 01, 2009, 04:04:19 am by Khem Caigan » Logged

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kaffemustasj
Gunner
**
Norway Norway


« Reply #2 on: June 29, 2009, 07:40:54 pm »

Thanks. So it seems I need some sort of a rectifier to get DC. Still, is it best to use a motor with low or high input requirement?
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Khem Caigan
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*******
United States United States


Aut Inveniam Viam Aut Faciam


WWW
« Reply #3 on: June 30, 2009, 07:31:59 am »

Thanks. So it seems I need some sort of a rectifier to get DC. Still, is it best to use a motor with low or high input requirement?


I suggest that you use whatever generator
that your engine is capable of spinning,
while providing a trickle of current to your
appliance ( lamp, &tc. ) or battery.

Cannibalizing an old radio- or lamp-generator
is one way to go - many of these devices
already incorporate a 3-volt generator into
their design.

I have a LifeLight from LifeGear, for example,
and it could work with a large/small gear ratio.

Or you could use a bicycle generator :

Bicycle Generator Overview
http://tinyurl.com/lb2lov

Bicycle Generator Circuit
United States Patent 4069451

Abstract:

A bicycle generator circuit is disclosed
for providing a regulated output voltage
to a bicycle mounted appliance.

The circuit includes a zener diode which
is coupled through input filtering and
limiting resistors to the output of the
bicycle generator to reduce the high peaks
of pulsating voltage from the ouptut of
the bicycle generator.

A rectifier is coupled through a filtering
and limiting resistor to the zener diode
to rectify the pulsating voltage to provide
an effective DC voltage and prevent reverse
leakage from the battery actuated appliance
when the generator is not in a charging mode.

A capacitor is coupled to the output of the
rectifier and across the output terminals
of the circuit to eliminate noise and
provide a smooth DC output voltage which is
coupled to the appliance to provide direct
energization and/or a charging voltage for
a battery actuated appliance.

Inventor:

Rouse, Paul S.
(103 N. Santa Anita Ave.,
Arcadia, CA, 91006)

Publication Date:
01/17/1978

Filing Date:
04/05/1976

http://tinyurl.com/kwfmvm

SINGLE CYLINDER HOT AIR ENGINE
With a 3 volt Generator

http://tinyurl.com/munelw
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Watson
Gunner
**
United States United States


« Reply #4 on: June 30, 2009, 08:20:22 am »

What you need to convert from AC to DC is a diode bridge, now you can design one using diodes, just buy a one peice diode bridge, or make one from scratch.

Also any motor will do some will be more efficient than others, but what you need is one with enough resistance to give your little mechanical engine some work, without stalling it outright. You can work around this whole deal with gear ratios. So essentially any motor you want will do.

I do not really suggest DC motors, because it's either a brush motor, which will likely not hold up to your machine, or it's an ac motor with a hidden diode bridge that you can't replace when stuff hits the fan.

I personally suggest you purchase an AC motor that you think looks sane, isn't ridiculously bigger than your mechanical engine.

I suggest you construct your own diode bridge using 4 diodes, the dark black ones with a silver band, not a zener diode, a zener diode might not live up to the voltage output. Think of them as like one way water valves ,and the silver dot or ring is the side the water "electricity" exits from.

http://en.wikipedia.org/wiki/Diode_bridge

the positive and negative are your outputs, and should be connected to whatever device you want to power, and each wire on the left should be connected to a wire from the motor
 

« Last Edit: June 30, 2009, 08:22:28 am by Watson » Logged

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OldProfessorBear
Zeppelin Overlord
*******
United States United States


Werebears RULE!


WWW
« Reply #5 on: June 30, 2009, 09:06:45 am »


Bicycle Generator Circuit
United States Patent 4069451

Abstract:

A bicycle generator circuit is disclosed
for providing a regulated output voltage
to a bicycle mounted appliance.

The circuit includes a zener diode which
is coupled through input filtering and
limiting resistors to the output of the
bicycle generator to reduce the high peaks
of pulsating voltage from the ouptut of
the bicycle generator.

A rectifier is coupled through a filtering
and limiting resistor to the zener diode
to rectify the pulsating voltage to provide
an effective DC voltage and prevent reverse
leakage from the battery actuated appliance
when the generator is not in a charging mode.

A capacitor is coupled to the output of the
rectifier and across the output terminals
of the circuit to eliminate noise and
provide a smooth DC output voltage which is
coupled to the appliance to provide direct
energization and/or a charging voltage for
a battery actuated appliance.

Inventor:

Rouse, Paul S.
(103 N. Santa Anita Ave.,
Arcadia, CA, 91006)

Publication Date:
01/17/1978

Filing Date:
04/05/1976

He got a patent for that? Bizarre.
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Khem Caigan
Zeppelin Overlord
*******
United States United States


Aut Inveniam Viam Aut Faciam


WWW
« Reply #6 on: June 30, 2009, 10:55:27 am »

He got a patent for that? Bizarre.

More or less :

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OldProfessorBear
Zeppelin Overlord
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United States United States


Werebears RULE!


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« Reply #7 on: June 30, 2009, 11:24:18 am »

He got a patent for that? Bizarre.

More or less :


Where's the innovation in that? Oh, never mind ...
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Khem Caigan
Zeppelin Overlord
*******
United States United States


Aut Inveniam Viam Aut Faciam


WWW
« Reply #8 on: June 30, 2009, 11:59:46 am »

Where's the innovation in that? Oh, never mind ...
If the patent process was solely about
innovation, we wouldn't have eedjits
patenting sections of genetic code,
now would we?

Sometimes it's all about privatizing
a bit of the commons.
« Last Edit: July 01, 2009, 04:06:39 am by Khem Caigan » Logged
kaffemustasj
Gunner
**
Norway Norway


« Reply #9 on: June 30, 2009, 07:24:10 pm »

Fixing a rectifier or diode bride would not be too much of a problem. But that does not matter, because I cant get the hold of an AC motor, at any reasonable price.
Therefore I think I will go for the solution where I use a bicycle dynamo. The store we have in Norway, which is meant to be much the same thing as Radioshack does not sell such things as bike dynamos, or loose AC motors and such (really!) Shocked
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Khem Caigan
Zeppelin Overlord
*******
United States United States


Aut Inveniam Viam Aut Faciam


WWW
« Reply #10 on: June 30, 2009, 08:42:35 pm »

The store we have in Norway, which is meant to be much the same thing as Radio Shack, does not sell such things as bike dynamos, or loose AC motors and such (really!) Shocked

I suggest that you try a sporting
goods store, such as Probike :

Probike
http://tinyurl.com/lcxhfd

And I wonder if it is possible for
you to do business with Amazon
in Norway?

Generator 12V 6W
Bicycle Light Power

@Amazon
http://tinyurl.com/llqwtd

Here are a few more links with
some project ideas :

Electrical Characteristics
of Bicycle Dynamos

http://tinyurl.com/mrw8un

Bicycle Dynamo Regulator
and Source Controller

http://tinyurl.com/nuzmrm

Regulator for a Hub Dynamo
http://tinyurl.com/mxc4go

A No-Friction Bicycle Dynamo
http://tinyurl.com/2qqj5m

Bicycle USB Charger
@RadUK
http://tinyurl.com/ngpfdz

How to Make a Bike Charger
for Your iPod!

by Mark Hoekstra
@geek technique
http://tinyurl.com/7hz92

Bicycle Dynamo Phone Charger
Products List

@PedalPower
http://tinyurl.com/ltez4o
« Last Edit: July 01, 2009, 04:01:48 am by Khem Caigan » Logged
kaffemustasj
Gunner
**
Norway Norway


« Reply #11 on: July 01, 2009, 08:03:59 am »

So now me best shot seems to be a bicycle dynamo.
Yes I am able to do business with amazon. I ordered How to build a time machine by Paul Davis, a couple of months ago Wink
If the technique used by geek technique, is just as easy as it seems (5.1v zener diode, 100 ohm resistor and a diode in series), I can build my own.

Now I have to start my quest looking for a dynamo so I wont have to order Smiley
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evand
Gunner
**
United States United States


« Reply #12 on: July 02, 2009, 03:27:58 pm »

So now me best shot seems to be a bicycle dynamo.
Yes I am able to do business with amazon. I ordered How to build a time machine by Paul Davis, a couple of months ago Wink
If the technique used by geek technique, is just as easy as it seems (5.1v zener diode, 100 ohm resistor and a diode in series), I can build my own.

Now I have to start my quest looking for a dynamo so I wont have to order Smiley

Basically, the specs on the motor won't change much when you run it as a generator.  So, first you want to determine what the output of your steam engine is.  How many watts, at what RPM?  It will have a maximally efficient RPM range for any given power output.  Determining this precisely would require a dynamometer and such, but I suspect you can get approximate answer without much trouble.  Possibly you even have a spec sheet Smiley

Then, you need to determine what voltage the thing you want to power requires, and how many watts it needs (which needs to be less than the steam engine output by a fair bit, efficiency won't be great).

Then you're ready to search for a motor + geartrain pair.  If you had a 12V, 1A load, and a steam engine capable of producing 18 watts at 600 RPM, you would want to find some pair of motor + gears that, if run as a motor at a bit over 12V would draw a bit over an amp and produce a bit over 12W of shaft output power at about 600RPM.  The precise numbers are hard to calculate without knowing the motor efficiency, unfortunately.  If you found a 3600 RPM 18V motor good for 15 watts output at 1 amp (83% efficiency) (just to put some numbers on it), you could approximate that as a 3 ohm series resistance and a perfectly efficient motor operating at 15V and 1A.  If you connected it with a 6:1 gear ratio to your 600 RPM steam engine, the (ideal) motor would output 15V and 1A, giving you 12V and 1A at the output of the real motor.

Of course, it all gets a little complicated -- if your load doesn't draw a full 1A, then the (mechanical) load that the motor presents to the steam engine will be lower.  If you don't control the throttle, the steam engine will tend to run faster at the lighter load, which will increase the voltage output of the motor.

OTOH, it's not as bad as it sounds -- you can install a regulator on the DC output, to turn the 14V you get into the 12V you need, for example.  Similarly, you can throttle the steam engine to control the output voltage (which will be roughly proportional to the actual RPM).  Note that motors are limited on RPM and torque, and similarly on input current, but not directly on power -- if you run the motor slower than nominal, you'll have to derate it accordingly.  OTOH, many AC motors have bearings that will happily run faster than the nominal speed as long as the side loads on the shaft are light, and you can get more than nominal power out of them (at higher than the nominal 60Hz line frequency).

An AC motor or a brushed DC motor will work.  In the AC case, you'll want a bridge rectifier.  In either case, you'll want to put a small film or ceramic capacitor directly on the motor (to reduce electrical noise), and a large electrolytic on the output of the rectifier to stabilize the DC output.

My suspicion is that unless 120V is ok, you'll have the easiest time finding a DC motor.  Of course, a low power 120AC motor might work fine, if you have a power supply for your design load that runs off that.  I recommend looking at surplus sites and such, and possibly junk yards.  Car door window motors and windshield wiper motors can be nice; you may have to remove the gearing if it's the wrong ratio or include a worm gear.  Another alternative to consider is a stepper motor -- because they have lots of poles, they can be good for low speed / high torque.  They have two coils, which would each need an independent bridge rectifier (or half bridge, if you get a unipolar motor with center-tapped coils).  They can be reasonably priced, but don't tend to be terribly high power or high efficiency.
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hatchleader
Snr. Officer
****
United Kingdom United Kingdom


Put the kettle on!!


« Reply #13 on: July 02, 2009, 05:47:55 pm »

I ordered How to build a time machine by Paul Davis, a couple of months ago Wink


*butts in to conversation with totally irrelevant comment*

Fantastic book!!!

*butts out again and runs into the distance with mods hot on his tail!!*
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^most likely a load of crap^

If in doubt hit it, if that doesn't work shoot it, and as a last resort blow it up!

Quote from: Bill Bailey
I'm English and as such crave disapointment
aquafortis
Officer
***
United Kingdom United Kingdom



« Reply #14 on: July 07, 2009, 09:51:49 pm »

Zener diodes are unsuitable for power rectification. They're signal devices really, for voltage reference and threshold triggering systems.

Using an AC motor may work if there is some residual magnetism in the rotor, but it's dodgy ground. A brushed AC motor may generate to some extent but getting a small one (less than 500 watts or so) is a mischief. AC motors are usually 3-phase induction or single phase shaded pole types with no brushes.

AC generators usually rely on residual or permanent magnetism in the rotor to kick it all off, and auxilliary rotor coils which are fed power from the stator coils, and regulated by a chopper circuit that cuts power if the stator output exceeds a preset limit. They're more complicated than motors.

With that said, a bicycle dynamo would be a good start - Permanent magnet, AC output, quite efficient due to no brushes and little low-speed mechanical resistance. As it is, voltage output will increase dramatically with increasing RPM, so either regulating the output voltage or regualting the engine speed would be a good idea.
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von Corax
Squire of the Lambda Calculus
Moderator
Immortal
*
Canada Canada

Prof. Darwin Prætorius von Corax


« Reply #15 on: July 08, 2009, 07:53:26 am »

Unless the laws of physics have changed since I was in high-school (in a previous century, so I suppose it's possible) a permanent-magnet DC motor run as a dynamo will produce pulsating direct current at a frequency proportional to the rotation speed, while a per-mag AC motor will generate alternating current, also at a frequency corresponding to the rotation speed. A motor with a wire-wound stator can operate as a generator if you apply an external "exciter" current to the stator coil, but that's probably far more complicated than you want if you've never done this before.

Rectifier diodes, or a bridge rectifier (four rectifier diodes in a single package) will convert AC to pulsating DC. If you already have DC, a rectifier will do nothing for you, unless you want to be able to reverse the dynamo without reversing the current. To turn the pulsating DC into flat DC you need a filter, usually a large capacitor connected across your generator output. A Zener diode connected across the generator output will act as a primitive voltage regulator/limiter, chopping the peaks off the voltage pulses but doing nothing to fill in the valleys (that's what the filter is for.) Using a Zener diode in place of a rectifier diode (or vice versa) will most likely cause the diode to give up its magic smoke.

As for suitable motors, I'm given to understand that the spindle motors from tape players or VCRs will generate a respectable zap.

Hope that's of some use to you.

Regards,

Prof. Darwin Prætorius von Corax

EDIT: Forgot to mention induction motors, which won't output anything at all when you spin the shaft.
« Last Edit: July 10, 2009, 11:50:27 pm by von Corax » Logged

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wbeaty
Deck Hand
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United States United States



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« Reply #16 on: July 23, 2012, 10:21:46 am »

DC DYNAMOS!   ...slowly I turned! step by step, inch by inch!

Quicky dynamo history:  Zenobe Gramme invented the modern dynamo: a wire-wrapped iron ring spinning between poles of a large horse-shoe magnet.


Thomas Edison started selling these like hotcakes.  Only one problem.  Edison was utterly convinced that long iron paths were better than short ones.  His commercial dynamos looked like this:





When Nikola Tesla spent a year redesigning Edison's DC machines, what did Tesla actually do?  Apparently we don't know.   But from the look of the designs he brought to Westinghouse, he probably converted Edison's dynamo stators into compact cylinder shapes.   In other words, he tried to kill off Edison's "Long Legged Mary-Anne" dynamos.  So, when Edison laughed about paying Tesla $50,000 for the work, and pretending it was all a joke, there may be other issues here.  Tesla's designs almost certainly made Edison look stupid.   (This was as bad or worse than trying to throw out Edison's wax cylinder phonograph and replace it with vastly improved flat-disc players.  We all know how that went!)  And Tesla's designs probably were worth far more than $50,000.

Tesla left, and Edison didn't obviously change any designs, so apparently he ignored the work Tesla had done.

Odd side note:  Some years later the Edison/Swan company in Europe (not under direct daily control of T. Edison,) decided that Edison's dynamo design was faulty.  They redesigned it based on Maxwell physics with much shorter iron path, which doubled the attainable wattage and improved the efficiency by 20X.   But they kept the "horse shoe" stator shape which eventually vanished into history: replaced by the compact cylinder designs pioneered by Westinghouse corp.

I conclude:  Tesla didn't only invent the induction motor.   He very probably invented all modern motors/generators everywhere:  if it's cylinder-shaped, then it's the remnants of Tesla crushing Edison during the AC vs. DC war:  a separate war between the long horse-shoe motors/dynamos versus cylinder-shape.

Either one might be fun to build.   Remember, light bulbs don't care if it's AC or DC, so no diodes needed if AC.

Here's the Westinghouse 1904 factory floor, no horse-shoe design philosophy visible:

Panoramic View Aisle B., Westinghouse Works


PS

Induction motors apparently can be used as generators, but they need a large value capacitor across them, where the value is chosen to produce 60Hz resonance with the motor coils.

Oh, on the OP's original questions:

For DC permanent-magnet motors, RPM is proportional to drive voltage.   If used as dynamos  ...same thing.   If you hook your motor up to XX voltage and it spins at a particular RPM, then if you use it as a dynamo, you need to spin it at that same RPM to generate that same voltage.

If you're powering flashlight incandescent bulbs, then figure out a drive-RPM which gives 3.0 volts.   (This might end up being a 24V fast-RPM motor which is then driven 8X slower by your engine.)

If building your own dynamo, then doubling the number of turns of wire will double the voltage.   Using neodymium magnets will increase the voltage by 5X to 10X.   Perhaps just stick small powerful magnets all over the rim of your engine flywheel, then place a spool of wire with iron core very close.  It will produce AC pulses as the magnets fly past the iron core.
« Last Edit: July 23, 2012, 10:41:18 am by wbeaty » Logged
phillroyal
Deck Hand
*
United Kingdom United Kingdom


« Reply #17 on: July 25, 2014, 12:57:53 am »

I have quite recently acquired a modell steamengine. It was a gift from my gf.
I tested it as soon as I had the possibility (which was yesterday, I am now getting ready for a new run Grin). Now, I really want it to power something, or rather give power to something.
To use a DC motor as a dynamo seems rather easy. So here comes my questions to you (and I have googled the subject several times), the wise people of brassgoggles:
1. Will the power generated from the motor/dynamo be AC?
2. What kind of motor will give the most output, 1.5v, 3v, 5v or 6v?
3. Is there anything I or some particular parts I should use to improve my output voltage?

Thank you for the help Grin
you can buy a generator for steam engines £18.00 0n ebay
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Peter Brassbeard
Zeppelin Captain
*****
United States United States



« Reply #18 on: July 25, 2014, 05:01:14 pm »

Small 3-phase synchronous AC motors have gotten a lot less expensive in recent years.  They find common use in modern electric powered RC aircraft.
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oldskoolpunk
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United States United States


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« Reply #19 on: July 26, 2014, 08:28:44 pm »


Small generator designed for use with model steam engines.
These are on eBay all the time; there are three for sale right now.  About $50 plus shipping.

As for motors as generators, small brush-type permanent magnet DC motors work fine as generators.  Little ones usually have only two poles, so they need to be rotated relatively fast. Find the motor's no-load speed, and use belts or gears to drive it at at least half that speed.

"Brushless DC" motors are really AC motors, usually 3-phase, and require external electronics to drive them. Permanent magnet brushless DC motors make great generators. Use a 3-phase diode bridge (six diodes) to get DC out. Brushless motors used in small quadrotors are great for this.  They tend to be very high RPM devices, and a model steam engine probably can't turn them fast enough.

Most small motors without permanent magnets will not do much as generators, unless you hook up a power source to energize the field winding. 
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